Typically, a part such as a throttle pedal in vehicles is mechanically connected to an engine throttle via a cable. However, in the latest vehicles, a throttle position sensor is mechanically connected to a throttle pedal and then generates an electrical output signal indicating the degree of pressing of the throttle pedal. This system is typically referred to as a “fly-by-wire” system.
In one type of throttle position sensor, a transmitting coil or an exciter coil is excited by a high-frequency source, and then the transmitting coil generates electromagnetic radiation. This transmitting coil is arranged in the shape of a circular pattern, but another pattern structure may be used instead of the circular pattern.
A receiver coil is arranged on a position sensor located near the transmitting coil. Therefore, when the transmitting coil is excited, the receiver coil generates an output signal due to inductive coupling to the transmitting coil.
In order to generate an output signal indicating the position of a throttle, a coupler element is rotatably mounted on a position sensor and is then rotated in synchronization with the pressing and release of the throttle pedal. The coupler element overlaps the positions of both the transmitting coil and the receiver coil. Consequently, inductive coupling between the transmitting coil and the receiver coil is varied when the coupler element is moved or rotated.
The output signal of the receiver coil generated due to such variation in inductive coupling is varied as a function of the angular position or linear position of the coupler element and the position of a part mechanically coupled to the coupler element.
However, the output signal of the receiver coil is apt to change due to a gap between the coupler element and the transmitting (or receiving) coil, which may occur due to a production deviation or the like.
The output signal of the receiver coil may be changed due to an error in the gap, and it is very important to correct such changes to detect accurate displacement.
Therefore, the requirement of a displacement sensor capable of correcting a gap error and then detecting displacement has been emphasized.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.